This invention relates generally to the salvage and scrap, and it is particularly applicable to systems which enhance the value of pieces of ferrous metals recovered from solid waste.
The inventor of the present invention and his assignee have been active for some years in the development of apparatus, methods and systems for treating solid waste in such manner that various components thereof can be reused. Typical U.S. Pat. Nos. illustrative of that activity include Baxter 3,549,092, Blakley et al 3,595,488, Marsh 3,714,038, Marsh 3,720,380, Marsh 3,736,223, Marsh 3,830,636, Marsh 3,945,575, Marsh 3,970,254 and Marsh 4,049,391. All of those patents have a general relation to the recycling of solid waste, with the end products including ferrous metals, aluminum and other non-ferrous metals, glass, reusable paper fiber, and fuel in several forms.
The present invention was developed with the objective of enhancing the recovery of ferrous metals as an improvement on the apparatus, methods and systems disclosed in the above listed patents. The disclosures of all of those patents have in common the basic aspects of a wet process for the treatment of solid waste in which the principal steps comprise delivering unsorted solid waste, in essentially asreceived condition, to a pulper wherein it is reduced to a slurry form while effecting segregation and separation from the slurry of the great majority of pieces of ferrous metal which resist the comminuting action of the pulping process. The pulped slurry is extracted from the pulper and treated in accordance with one or more of the listed patents to effect separate recovery of aluminum, glass, fiber, and organic residue suitable for conversion to fuel and other end products.
The present invention was developed with particular relation to recovery of the ferrous metal pieces which are separated from the slurry during the pulping process. In general, the majority of these pieces can be classified as one of three shape categories, namely flat shapes comprising predominantly steel cans and the like which have been flattened by the action within the pulper, chunky shapes of generally clindrical, spherical or block-like configuration, and long thin shapes such as pieces of pipe, rod, stiff wire and the like.
In addition to the shapes which characterize each of these categories, the categories differ from each other in the metallurgy of their component pieces. Thus in the flat shape catagory, the predominant components are tin plated cans, and the chunky category also contains substantial quantities of tin plate in the form of large cans and pieces of sheet metal which have been formed into ball shapes by the rotor action in the pulper. On the other hand, the rod-like pieces, plus the occasional large chunky or block-like pieces, are generally of cast iron or steel of maximum value as scrap.
The factors just discussed dictate that if the different shapes of metal pieces can be sorted into appropriate categories prior to their disposal for reclamation as scrap, they will have correspondingly increased value. Prior to the present invention, however, no commercially available equipment has been found which will effectively separate flat pieces from rod-like pieces, nor which will effectively separate flat pieces from generally spherical or cylindrical pieces having comparable maximum dimensions.